I don't know about your IP addresses, but, people can use my IP addresses from a number of locations which are nowhere near the jurisdiction in which my network operates, so, I don't really see the correlation here with license plates or phone numbers.
I'm not clear if you mean legitimately here, or not. If you've authorised people to relay traffic through you in some way, you'd be the right first contact. If you're talking about unauthorised spoofing, it's a lot like the first two cases (I'd say a fair bit easier / cheaper than the second, not substantially more so than the first).
In my case, yes, 100% legitimately. I can be contacted, but, the reality is that I don't track it. I am no longer in direct contact with a number of people who have legitimate use of my IP addresses. If I find them doing something I consider abuse, then, I'll turn off the access. However, I don't maintain contact information or the ability to personally identify the correlation between the person and the access. So far, abuse has been rare enough that this has not been an issue. I've had to turn off two services I used to provide as a result of abuse in approximately 20 years of operating a network here. Owen